stub_factory: correctly require luassert.mock
stub_factory: correctly require luassert.mock

otherwise it's just an undefined global here because this is not
busted _spec file.

Signed-off-by: Gregory M. Turner <1f6d1f05bf03ff30afa6123e0bee2caa2da7cff0@be-evil.net>

Afforess/Factorio-Stdlib